1. Field of the Invention
This invention is generally directed to chemical and biochemical analysis for an analyte in a fluid or gaseous mixture, and more specifically concerns a multiple event sensor for performing analysis of multiple analytes, and a method of manufacturing the multiple event sensor.
2. Description of Related Art
Measurement of acidity (pH) and the tension or partial pressure of carbon dioxide and oxygen in the blood have become particularly important in modern medicine in determining the respiratory status of a patient. Optical sensors have been developed which are based upon the principle of quenching of the fluorescence reaction of certain dye indicators in the presence of the analyte of interest. The fluorescent indicator is typically immobilized within a permeable membrane on the end of an optical fiber utilized in measuring the intensity of the fluorescence reaction of the indicator at a certain emission wavelength. Another optical fiber may also be used to carry a certain wavelength of light to initiate the fluorescence of the indicator, although it is possible to reduce the size of the sensor by using the same optical fiber for conducting the different wavelengths of fluorescence and excitation light.
Although a fiber optic fluorosensor for oxygen and carbon dioxide has been developed which includes a first indicator layer sensitive to oxygen and a second indicator layer sensitive to carbon dioxide on a single optical fiber, such multiple layer optical fiber sensors can be difficult to manufacture, and there is a concern that such an arrangement of indicator layers may interfere with the sensitivity of one or more of the indicator layers in the sensor. A triple sensor for blood pH, pCO.sub.2, and pO.sub.2 has also been developed which includes three separate optical fibers having appropriate indicator layers at their ends, but possible cross-interference of the individual sensor layers on ends of the optical fibers remains a matter of concern; and overlap of the ends of the optical fibers which tend to be the thickest portion of the optical fiber sensors, affecting the shape of the sensor, tends to increase the risk of development of thrombus buildup with intravascular use of the device.
Hence, it would be desirable to provide a multiple blood gas sensor which combines various , individual proven sensors into a single apparatus which minimizes cross-interference of individual sensors within the apparatus, and achieves a shape which minimizes turbulence of blood as it flows by the device when it is used intravascularly.